Typical wireless power transmission systems include power transmission systems using magnetic field coupling, which transmit electric power from primary coils in power transmission apparatuses to secondary coils in power reception apparatuses by using the magnetic fields. Since the magnitudes of magnetic fluxes passing through the respective coils have large effects on the electromotive forces in the transmission of the electric power using the magnetic field coupling in such systems, high precision is required for the relative positional relationship between the primary coils and the secondary coils. In addition, it is difficult to reduce the apparatuses in size because of the use of the coils.
In contrast, wireless power transmission systems using electric field coupling, such as the ones disclosed in PTLs 1 and 2, are also known. In such a system, electric power is transmitted from coupling electrodes in the power transmission apparatus to coupling electrodes in the power reception apparatus through the electric field. The relative positional precision required for the coupling electrodes is relatively low in this method and it is possible to reduce the coupling electrodes in size and thickness.
FIG. 1 illustrates the basic configuration of the power transmission system described in PTL 1. This power transmission system is composed of a power transmission apparatus and a power reception apparatus. The power transmission apparatus includes a high-frequency high-voltage generating circuit 1, a passive electrode 2, and an active electrode 3. The power reception apparatus includes a high-frequency high-voltage load circuit 5, a passive electrode 7, and an active electrode 6. The active electrode 3 in the power transmission apparatus is close to the active electrode 6 in the power reception apparatus via a gap 4 to cause the active electrode 3 in the power transmission apparatus to be electrically coupled to the active electrode 6 in the power reception apparatus.
The passive electrode 2 in the power transmission apparatus, the active electrode 3 in the power transmission apparatus, the active electrode 6 in the power reception apparatus, and the passive electrode 7 in the power reception apparatus are arranged so as to be parallel to each other.
In the power transmission system described in PTL 2, the power transmission apparatus includes a first resonant circuit that resonates with an alternating current signal generated by an alternating current signal generator and a feeding electrode. The power reception apparatus includes a power reception electrode that generates an electrical signal, a second resonant circuit that resonates with the electrical signal, a rectifier that generates direct current power from the electrical signal subjected to the resonance, and a circuit load. An active electrode in the power transmission apparatus is provided on the same plane as that of a passive electrode therein. An active electrode and a passive electrode in the power reception apparatus are provided so as to oppose the corresponding active electrode and passive electrode in the power transmission apparatus across a certain space.
FIGS. 18 to 21 in PTL 2 show that the active electrode at the power reception apparatus side is composed of multiple split electrodes and the split electrodes in the power reception apparatus overlapping with first and second active electrodes in the power transmission apparatus when the power reception apparatus is placed on the power transmission apparatus selectively operate as the active electrodes.
PTL 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-531009
PTL 2: Japanese Unexamined Patent Application Publication No. 2009-296857